1. Field of the Invention
The present invention relates to a control technology that outputs a video signal based on auxiliary information associated with the video shot-change.
2. Description of the Related Art
Conventionally, in a display apparatus and a video processing apparatus, for various purposes, image data associated with an input video signal is stored in a frame memory, and a video signal is output or displayed by reading out data from this memory. In this context, when a video signal is read out asynchronously to the frame frequency of the input video signal, there are cases in which the information of different frame images mixes in one frame. In the case in which a video changes significantly between different frames, development in which what appear to be vertical bands are visible (what is termed “tearing”) occurs in the video, and this becomes a hindrance to viewing. Here, tearing will be explained with reference to FIG. 4A to FIG. 4C. FIG. 4A shows an example of a frame image of an input video signal, and FIG. 4B shows an example of a frame image of a video signal that is input after FIG. 4A. In addition, FIG. 4C shows an example of an image of data wherein data of the frame image of FIG. 4B has been read out from the frame memory while the data of the frame image of FIG. 4A is being written to the frame memory. The upper half portion of the image in FIG. 4B is rendered in the upper portion, where the broken line serves as a boundary, and the lower half portion of the image in FIG. 4A, which is the preceding frame image, is rendered in the lower portion. In this manner, development in which a boundary at which images of different frames are rendered is produced is tearing, and this is caused by the data of the temporally adjacent frame images being read out asynchronously to the frame frequency, as shown in FIG. 4C.
For this state, a technology is known in which the occurrence of tearing is prevented by synchronizing the reading out of the image data with the frame frequency of the input video signal by suitably adjusting the phase. Specifically, a technology (below, referred to as “frame lock”) has been implemented in which frame image data is read out after being synchronized with a vertical synchronizing signal of the video signal. In addition, a technology (what is termed “double buffering”) is known in which the timing of the writing and reading of a plurality of image data with respect to frame memory is suitably controlled. In the later technology, although tearing can be suppressed, suppressing the number of times that each frame image is read out from being different or the presence of unread frames is difficult.
In addition, from a different point of view, a technology has been implemented in which a plurality of image data is composed and output or displayed. Here, an example of the composition of image data will be explained with reference to FIG. 5. Images A and B shown in FIG. 5 show examples of images associated with video signals before syntheses, and images C and D each show examples of an images that is output or displayed after composition. Image C exemplifies a configuration (called, for example, “side by side” and the like) in which images A and B are arranged side by side in a horizontal direction. In addition, image D exemplifies a configuration (called, for example, “picture in picture” and the like) in which image A is rendered in a main screen and image B is rendered in a sub-screen. In addition to these, composing processing associated with video signals is implemented in various combinations. For example, in a display apparatus, a manner of use in which a television program is displayed in a sub-screen while displaying a working screen in a computer device, becomes possible, and thus, the usability for a user is improved. However, in the case of composing processing of image data, even if frame locking is carried out on any of the video signals, there is a condition in which suppressing the occurrence of tearing is difficult at a portion at which the data associated with other video signals has been composed. Laid Open Unexamined Japanese Patent Application 2007-271848 discloses a method in which, in a video output apparatus that generates and outputs a single display video based on a plurality of input videos, a frame frequency of the output video is selected from among the input video and set according to predetermined selection rules.
Laid open Japanese Patent Application No. 2007-271848 discloses a method in which a video signal that is an object of synchronization is directly selected by the user. However, in this case, because a user must have suitable knowledge, there is a possibility that the most suitable function is not effectively utilized or that the operation is laborious for the user. In addition, Laid Open Japanese Patent Application No. 2007-271848 also shows a method in which an input video signal, in which the area of the displayed image is large, is made a synchronized object with priority, but this selection rule has no relation to the possibility that tearing may occur. Thus, in the case in which tearing has occurred, there is a concern that the viewing of the user may be hindered. In addition, a method is disclosed in which the input video signal for which the illumination change of the video content between frames is largest is set as the synchronization object. In this method, when the video signal that is to be made a synchronization object cannot be selected unless a shot-change in the video content has occurred, a video signal that should be made the synchronization object cannot be selected, and thus, there is a possibility that the influence on an image due to a deterioration such as tearing will be viewed by the user. Furthermore, a processing load is applied because processing in which the shot-changes in the video content is measured is necessary.